Method and compositions for inhibiting corrosion



United States Patent 3 230 173 METHOD AND coMPo'srrIoNs FOR INHIBITING CORROSION John D. Spivack, Spring Valley, N.Y., assignor to Geigy Chemical Corporation, Ardsley, N.Y. No Drawing. Filed May 3, 1962, Ser. No. 192,083 14 Claims. (Cl. 252148) This application is a continuation-in-part of copending application Serial No. 831,019, filed August 3, 1959, now US Patent No. 3,048,620, which in turn is a continuation-ain-part of copending application Serial No. 777,587, filed December 2, 1958, now US. Patent No. 3,151,160.

The present invention relates to the inhibition of corrosion of metal in contact with aqueous solutions, by incorporating in said solutions an effective quantity of a corrosion inhibitor of the formula wherein R represents an alkyl group, such as an alkyl group having from 6 to 18 carbon atoms inclusivee.g., hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl-preferably an alkyl group having from 8 to 18 carbon atoms such as octyl, dodecyl, octadecyl, and R represents either hydrogen or lower alkyl.

In particular this invention relates to preventing corrosion of iron in contact with aqueous solutions. Very often it is necessary for iron equipment to come in contact with aqueous solutions. It is advantageous to prevent undue rusting and corrosion of this iron by incorporating in the solutions sufiicient amounts of a corrosion inhibitor. For example in aqueous systems a sufficient quantity of the inhibitor of the invention is dissolved in the solution which is in contact with the iron or steel equipment such as piping, pumps, storage containers, etc. In general, the necessary amount of inhibitor may range from about 0.01% by weight to about 10% by Weight of the solution, the corrosive action of which is to be inhibited. In the preferred embodiment, solutions having a pH less than 7 are protected against corrosive action when in contact with iron, steel, etc. The method of the invention is effective over a broad range of temperatures from about 0 C. to 100 C. at normal pressure and, at superatmospheric pressures, the method may be used for solution temperatures up to 200 C. or higher. Such higher temperatures and pressures may be present in welldrilling operations where the acid solution has a tendency to cause corrosion in the pipes, casings, and other equipment.

The invention also relates to certain novel inhibitor compounds such as compounds of the formula wherein R represents lower alkyl-phenyl or phenyl. In this specification wherever lower alkyl is mentioned it is understood that an alkyl group having from 1 to 6 carbon atoms inclusive is represented,

The tertiary-amino alkylated amides according to the present invention can be obtained in several ways. One method involves the addition of an amine to an Dali-11H saturated amide, nitrile or ester, or carboxylic acid. The amide is obtained directly when the 04,,8-111'1S3tt113t6d amide is employed. In using the nitrile, the amide endproduct is obtained on hydrolysis of the nitrile group of the intermediate. The use of the a,fl-unsaturated ester involves the reaction of the intermediate tertiary amino alkyl carboxyl ester with ammonia to yield the desired tertiary amino alkyl carboX-amide. The following reaction schemes illustrate these methods:

l NHa I Hydrolynls In the foregoing and subsequent illustrations R and R are as hereinbefore defined.

An alternate method for the production of the tertiary amino alkylated amides according to the present invention involves adding to an nip-unsaturated amide, ester, acid or salt thereof, or nitrile, a suitable carbamoyl alkyl, carbalkoxyalkyl or cyano alkyl secondary amine. The following reaction scheme is illustrative of this method:

R NHal f CHzCHC ONH;

RIN R OHzCHC ONH:

Hydrolysis I As hereinbefore set forth, the use of the nitrile of ester requires subsequent reaction of said nitrile or ester by hydrolysis or amidification with ammonia, respectively, in order to obtain the tertiary amino alkylamide.

In the foregoing alternate method of synthesizing the tertiary amino alkylamides of the present invention, the c p-unsaturated compound may be replaced by a suitable halogen compound or sulfate such as the following:

r 3 wherein R is as hereinbefore defined, M is hydrogen, alkali metal, or the ammonium radical, and X is halogen or OSO H. The following reaction scheme illustrates the use of these compounds:

Thus, the tertiary-amino-bis-propionamide can be produced by suitable substitution reactions, as well as by addition reactions as hereinbefore set forth.

In the foregoing methods of synthesis it is understood that many other suitable starting materials, not specifically named, may be usefully employed in the practice of the present invention. For example, any suitable primary amine may be used as starting material, such as primary saturated aliphatic amines containing from 6 to 18 carbon atoms. Thus, hexylamines, heptylamines, octylamines, nonylamines, decylamines, tetradecylamines, hexadecylamines, octadecylamines may be used.

Similarly, suitable carbamoylalkyl secondary amines, as well as carbalkoxyalkyl and cyanoalkyl secondary amines may be employed. Thus, the corresponding hexyl-, hepty1-, octyl, nonyl-, decyl-, tetradecyl, hexadecyl-, octadecyl-derivatives of these secondary amines may be suitably employed.

Furthermore, phenyl and alkylphenyl amines, such as aniline, etc. may be advantageously employed.

Particularly suitable a e-unsaturated compounds for use in this invention are the acrylamides, and methacrylamides. The a,,8-unsaturated esters such as methylacrylate, ethylacrylate, and the methacrylates are also very useful. Acrylonitrile and methacrylonitrile are also particularly suitable u.,/i'-unsaturated nitriles for the practice of this invention.

Still another method of obtaining the tertiary amino reaction of alkylated amides of the present invention involves alkylating agents such as alkyl halides or sulfates with suitable iminodiesters, iminodicarboxy-acids, iminodicarboxamides or dinitriles. Any suitable halide, moreover, may be used. For example, the chlorides: hexyl chloride, octyl chloride, dodecyl chloride, tetradecyl chloride, hexadecyl chloride, octadecyl chloride, and also the bromides: hexyl bromide, octyl bromide, dodecyl bromide, tetradecyl bromide, hexadecyl bromide, octadecyl bromide, can be used advantageously.

Suitable sulfates may also be used. Thus, hexyl acid sulfate, lauryl acid sulfate, octadecyl acid sulfate may be used,

This method is especially advantageous when the same groups are the substituents of the disubstituted secondary amine starting material of this method. Moreover, the desired amide is obtained directly when its substituted amino-alkyl carboxamide is employed. Additional steps are required when suitable esters or nitriles are employed as hereinbefore set forth. Of course, if the imino carboxyacid is used, then subsequent amidification is required. The following scheme of reactions illustrates the use of these alkylating agents in the present invention, without limiting the same thereto:

lNHa Heat The present invention is illustrated by the following 7 Example 1.-2-ethylhexylamine-bis-propionamide 130 parts of 2-ethylhexylamine are added dropwise over a period of about 20 minutes at 10 to a solution of 166.5 parts of acrylamide (2.3 moles) in 500 parts by volume of ethanol. The reaction mixture is heated while stirring at 90 for 6 hours. The resultant mixture is then concentrated by distilling off the ethanol at 15 mm. Hg pressure. The residual light yellow oil is dissolved in ether, freed of precipitated excess acrylamide by suction filtration, the ether being removed by distillation at atmospheric pressure and finally at 1.5 mm. Hg pressure. Analysis of the light yellow oil indicates that it consists of 93.3% 2-ethylhexylirnino-bis-propionamide.

Example Zfn-dOdecylimino-bis-propionamide 185 parts of n-dodecylamine (1.0 mole), dissolved in 70 parts of methanol, are added dropwise at 9 to 11 to a solution of 166 'parts of acrylamide (2.3 moles) in 500 parts of methanol while stirring.

The reaction mixture is then heated at 65 while stirring for 16 hours. 100 parts by volume of methanol are then added and the reaction mixture is allowed to crystallize spontaneously. The n-dodecylamino-bis-propionamide, in form of white crystals, is filtered oif, dried in vacuum at 100 mm. Hg pressure at 60. 274.5 parts are obtained (yield of 81.5%). The white crystals melt at 116 to 117.

Analysis.Nitrogen (Dumas) percent. Calculated for C H N O 12.84. Found: 12.41. Basic nitrogen equivalent weight. Calculated: 327. Found: 327.

Example 3.-Octadecylimin'o-bis-propionamide 177.5 parts of acrylamide (2.5 moles) are dissolved in 400 parts by volume of methanol. To this methanolic acrylamide solution is added, at 10, a solution of 269 parts of n-octadecylamine dissolved in 500 parts by volume of methanol. The reaction mixture is warmed up to about 30, whereupon a moderately exothermic reaction ensues, the temperature rising to 50. When the reaction temperature begins to fall, the reaction mixture is heated at reflux for 9 hours. The reaction mixture is allowed to cool spontaneously to room temperature. The crystal slurry is diluted with an additional 400 parts by volume of methanol and the crystals filtered and dried. 373 parts of octadecylimino-bis-propionamide is thus obtained (yield of theory). Octadecylimino-bis-propiionamide is a White crystalline solid melting at 113 to 1 5.

Analysis.-Nitrogen (Kjeldahl) percent. fQI CHHQQNQOZZ Found: 10.10.

Calculated Example 4.Anilino-bis-propionamide 93 parts of aniline are dissolved in 150 parts by volume of glacial acetic acid, the solution being heated to about 85. 158 parts of acrylamide are added to the acetic acid solution over a period of 45 minutes; the addition reaction is exothermic and is held to a maximum temperature of 120 by removing the heat source and controlling the rate of addition. After complete addition of the acrylamide, the reaction mixture is heated at 80 to 82 for about 6 hours. The reaction mixture so obtained is diluted with 250 parts of water and made alkaline with aqueous sodium hydroxide. The resulting tan precipitate is filtered off and dried; it consists of 198 parts of anilino-bis-propionamide of about 95% purity, representing a yield of 80% of theory. Upon recrystallization from dioxane the anilino-bis-propionamide is obtained as white crystals, melting at 152 after drying.

Analysis.-Nitrogen (Dumas) percent. Calculated for C12H17N302i Found:

If, in Example 4, p-methylphenylamine is used instead of aniline, then p-methylphenylirnino-bis-propionarnide is obtained. Similarly, starting with p-ethylphenylamine, p-ethylphenylimino-bis-propionamide is obtained.

INHIBITION OF CORROSION Example 5 0.25% of n-dodecylimino-bis-propionamide is incorporated into hydrochloric acid solution (10% by weight of concentrated reagent hydrochloric acid dissolved in Water). The so obtained solution is then heated to 70 and cleaned weighed specimens of cold-rolled steel are introduced into this solution. After four hours at this temperature in the solution the steel specimens are removed, brushed, rinsed, dried and reweighed. The percent protection is calculated from the weight loss to determine protection against corrosion as follows: Percent protection equals 100 times weight loss of blank minus weight loss of test sample divided by loss of blank. Thus, for n-dodecylimino-bis-propionamide a percent protection of 95.5% is obtained.

If in Example 5, n-octadecyl-bis-propionamide is employed in place of n-dodecylimino-bis-propionamide then 93.5% protection is obtained.

An acidic water system used in oil and gas producing wells is inhibited against corrosion of the ferrous piping, casings, pumps, valves, etc. by introducing into the well water about 0.5 percent by weight of 2-ethylhexyliminobis-propionamide.

Incorporation into the well water of 0.5% by weight of octadecylimino-bis-propionamide also reduces corrosion in the oil and gas well.

Example 5 illustrates the utility of the compounds of the invention in acid pickling of mild steel.

What is claimed is:

1. The method of inhibiting aqueous ferrous corrosion which comprises contacting the ferrous surface with a corrosion medium containing, in an amount sufficient to inhibit corrosion, a compound of the formula:

R wherein R is a member selected from the group consisting of alkyl with from 6 to 18 carbon atoms inclusive, phenyl and lower alkylphenyl, and R is a member selected from the group consisting of hydrogen and lower alkyl.

2. The method of claim 1, wherein said inhibitor is a tertiary-amino alkylated compound of the formula:

CHzCHzC ONHz CHzCHzC ONHg wherein R is an alkyl group with from 1 to 18 carbon atoms inclusive.

3. The method of claim 1, wherein said inhibitor is a tertiary-amino alkylated compound of the formula:

CHZCH CONH CHzCHzC ()NHz wherein R is a member selected from the group consisting of alkyl with from 6 to 18 carbon atoms inclusive, phenyl and lower alkylphenyl, and R is a member selected from the group consisting of hydrogen and lower alkyl.

9. A composition according to claim 8, wherein said inhibitor is a tertiary-amino alkylated compound of the formula:

CHzCHzC ONE:

CHgCHzC ONHg wherein R is an alkyl group with from 1 to 18 carbon atoms inclusive.

10. A composition according to claim 8, wherein said inhibitor is a tertiary-amino alkylated compound of the formula:

CHzOHzC ONHg OHzCHzC ONE:

wherein R is lower alkylphenyl.

11. A composition according to claim 8, wherein said inhibitor is Z-ethylhexylimino-bis-propionamide.

12. A composition according to claim 8,. wherein said inhibitor is n-dodecyliminmbis-propionamide.

13. A composition according to claim 8, wherein said inhibitor is anilino-bis-propionamide.

14. A composition according to claim 8, wherein said inhibitor is octadecylimino-bis-propionamide.

References Cited by the Examiner UNITED STATES PATENTS 2,368,604 6/1945 White 252-392 2,411,662 11/1946 Martin et al. 260561 2,461,509 2/1949 Harvey et al 260558 2,658,076 11/1953 Krimmel 260-558 2,790,780 4/1957 Spivack et al 252-392 2,844,629 7/ 1958 Bruce et al 260561 2,877,187 3/1959 Henderson et al 260-561 3,017,355 1/1962 Oakes 2528.55 3,044,958 7/ 1962 Newsom 2528.55 3,048,620 8/ 1962 Spivack 252392 JULIUS GREENWALD, Primary Examiner. 

1. THE METHOD OF INHIBITING AQUEOUS FERROUS CORROSION WHICH COMPRISES CONTACTING THE FERROUS SURFACE WITH A CORROSION MEDIUM CONTAINING, IN AN AMOUNT SUFFICIENTR TO INHIBIT CORROSION, A COMPOUND OF THE FORMULA:
 8. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF AN ACIDIC AQUEOUS CORROSIVE MEDIUM CONTAING, IN AN AMOUNT SUFFICIENT TO INHIBIT FERROUS CORROSION, AN INHIBITOR OF THE FORMULA: 